Tungsten films were deposited on silicon and SiO2 by the SiH4 and H2 reduction of WF6. The stress, grain size and microstructure of the deposits were investigated to find the major factors affecting the adhesion. The deposited tungsten films under our experimental conditions have tensile stress. Tungsten films on silicon and SiO2 have a micropore structure. The grain size increases with the deposition temperature. The adhesion was measured by both tape and scratch tests to obtain quantitative data. The peel strength is inversely proportional to the residual tensile stress.